# LDAP authentication

LDAP is an open standard for querying and modifying directory services that is commonly used for authentication, authorization and accounting (AAA). OMERO.server supports the use of an LDAP server to query (but not modify) AAA information for the purposes of automatic user creation.

This allows OMERO users to be automatically created and placed in groups according to your existing institution policies. This can significantly simplify your user administration burden. Note that OMERO has its own concept of “groups” that is quite distinct from LDAP groups.

The OMERO.server LDAP implementation can handle a number of use cases. For example:

- Allow every “inetOrgPerson” under `omero.ldap.base` to login

- but restrict access based upon an arbitrary LDAP filter, e.g.

    omero.ldap.user_filter=(memberOf=cn=someGoup,ou=Lab,o=College)

- and add that user to some number of groups, e.g.

    omero.ldap.new_user_group=:query:(member=@{dn})

## How it works

On login, the username provided is searched for in OMERO. If the name does not exist, then the LDAP plugin is queried for a username matching the system-wide user filter. If such an LDAP entry exists and the password matches, a new user with the given username is created, and the user is added to any groups which match the `new_user_group` setting.

On subsequent logins, the user filter and the password are again checked against the LDAP server, and if there is no longer a match, login is refused. If you would prefer to only have the `user_filter` applied during user creation and not on every login, see Legacy password providers.

You can take existing non-LDAP users and ‘upgrade’ them to using LDAP with the OMERO command line tool, see Converting non-LDAP users to LDAP authentication. You can also use omero ldap create to add an ldap user to OMERO groups without requiring them to log in first, see User/group management for details.

## LDAP properties

The LDAP plugin is configured via several configuration properties, all starting with `omero.ldap` (see LDAP).

Some of the property values are passed directly to the underlying LDAP library (Spring LDAP), which in turn makes use of the Java API. OMERO does not modify the error messages thrown by the library or by Java, so please consult the appropriate documentation to diagnose any low-level problems.

Note

Please remember that once a change has been made, a server restart will be needed.

### Minimum configuration

The following properties are the minimum requirements for logging in to OMERO using LDAP.

    omero.ldap.config=true
    omero.ldap.urls=ldap://localhost:389
    omero.ldap.username=
    omero.ldap.password=
    omero.ldap.base=ou=example,o=com

After having configured your connection, you can turn LDAP on and off between restarts by setting `omero.ldap.config` to false. The `base` property determines where in the LDAP tree searches will begin. No users or groups will be found if they are not under the base provided.

### User lookup

Two user properties are used to look up users by login name and, if necessary, create new users based on the information in LDAP.

    omero.ldap.user_filter=(objectClass=person)
    omero.ldap.user_mapping=omeName=cn,firstName=givenName,lastName=sn,email=mail,institution=department,middleName=middleName

`omero.ldap.user_filter` will be AND’ed to the username query, and can contain any valid LDAP filter string. The username query is taken from the LDAP attribute which gets mapped to “omeName” by `omero.ldap.user_mapping`. Here, the “cn” is mapped to “omeName”, so the username query is `(cn=[login name])`. The final query is `(&(objectClass=person)(cn=[login name]))`, which must return a single result to be considered valid.

### Group lookup

Three group properties are all concerned with what groups a user will be placed in on creation.

    omero.ldap.group_filter=(objectClass=groupOfNames)
    omero.ldap.group_mapping=name=cn
    omero.ldap.new_user_group=default

The group filter and group mapping work just as the user filter and mapping do, in that the group name query will be AND’d with the `group_filter`. In this case, the final query would be `(&(objectClass=groupOfNames)(cn=[group name]))`. However, these properties may not be used depending on the value of `new_user_group`, which can have several different values:

- If not prefixed at all, then the value is simply the name of a group which all users from LDAP should be added to.

- If prefixed with `:ou:`, then a user’s last organizational unit (OU) will be used as his or her group. For example, the user with the DN “cn=frank,ou=TheLab,ou=LifeSciences,o=TheCollege” will be placed in the group “TheLab”.

- If prefixed with `:attribute:`, then the rest of the string is taken to be an attribute all of whose values will be taken as group names. For example, `omero.ldap.new_user_group=:attribute:memberOf` would add a user to all the groups named by memberOf. You can prefix this value with `filtered_` to have the `group_filter` applied to the attribute values, i.e. `:filtered_attribute:memberOf` will mean that only the values of memberOf which match `group_filter` will be considered. An example value of the `memberOf` attribute would be: `CN=mygroup,OU=My Group,OU=LabUsers, DC=openmicroscopy,DC=org`

- If prefixed with `:dn_attribute:`, then the rest of the string is taken to be an attribute all of whose values will be taken as group distinguished names. For example, `omero.ldap.new_user_group=:dn_attribute:memberOf` would add a user to all the groups named by memberOf, where the name of the group is mapped via `group_mapping`. You can prefix this value with `filtered_` to have the `group_filter` applied to the attribute values, i.e. `:filtered_dn_attribute:memberOf` will mean that only the values of memberOf which match `group_filter` will be considered. An example value of the `memberOf` attribute would be: `CN=mygroup,OU=My Group,OU=LabUsers, DC=openmicroscopy,DC=org`

  Note that if an attribute specified in `omero.ldap.group_mapping` does not constitute a part of the Distinguished Name (DN) as determined by your LDAP server then it can only be found by using `:attribute:` or `:filtered_attribute:` instead. Typical attributes that comprise the DN are: DC, CN, OU, O, STREET, L, ST, C and UID.

- If prefixed with `:query:`, then the rest of the value is taken as a query to be AND’ed to the group filter. In the query, values from the user such as “@{cn}”, “@{email}”, or “@{dn}” can be used as place holders.

- If prefixed with `:bean:`, then the rest of the string is the name of a Spring bean which implements the NewUserGroupBean interface. See the developer documentation LDAP plugin design for more info.

### Compound Filters

Note

OMERO uses standard RFC 2254 LDAP filters, so they must conform to that syntax and are only able to do what those filters can do. You can test the filters via ldapsearch on your OMERO server (assuming you have the OpenLDAP binaries installed).

If you are using OpenLDAP make sure your directory has the `memberOf` attribute correctly configured. Some versions of ApacheDS do not support `memberOf` at all.

Both the `user_filter` and the `group_filter` can contain any valid LDAP filter string. These must be a valid filter in themselves. e.g.

    omero.ldap.user_filter=(|(ou=Queensland Brain Institute)(ou=Ageing Dementia Research))

The “|” operator (read: “OR”) above allows members of two organizational units to login to OMERO. Expanding the list allows concentric “rings” of more and more OU’s granular access to OMERO.

    omero.ldap.group_filter=(&(objectClass=groupOfNames)(mail=omero.flag))

The “&” operator (read: “AND”) produces a filter that will only match groups that have the `mail` attribute set to the value `omero.flag`. When combined with the `group_mapping`, the final query would be `(&(&(objectClass=groupOfNames)(mail=omero.flag))(cn=[group name]))`

This is the same as the query `(&(objectClass=groupOfNames)(mail=omero.flag)(cn=[group name]))` but setting `group_filter` to `(objectClass=groupOfNames)(mail=omero.flag)` is not valid as that is not a valid filter on its own.

To restrict the list of groups to just the ones returned by the above query, the following setting is also required to remove unmatched groups:

    omero.ldap.new_user_group=:filtered_dn_attribute:memberOf

## Case sensitivity

By default, the LDAP plugin is case-sensitive i.e. it will treat the usernames JSmith and jsmith as two different users. You can remove case sensitivity using:

    omero config set omero.security.ignore_case true

Warning

Enabling this option will affect all, even non-LDAP, usernames in your OMERO system. It is the system administrator’s responsibility to handle any username clashes which may result. Making non-LDAP usernames lowercase is required. Non-LDAP users with uppercase characters in their username will not be able to log in and will not appear in some administrative tools.

`UPDATE experimenter SET omename = lower(omename);` can be used on your database to make this change to all users if desired. This operation is irreversible.

## LDAP over SSL

If you are connecting to your server over SSL, that is, if your URL is of the form `ldaps://ldap.example.com:636` you may need to configure a key and trust store for Java. See the Server security and firewalls page for more information.

## Synchronizing LDAP on user login

This feature allows for LDAP to be considered the authority on user/group membership. With the following setting enabled, each time a user logs in to OMERO their LDAP groups will be read from the LDAP server and reflected in OMERO:

    omero config set omero.ldap.sync_on_login true

Admin actions carried out in the clients may not survive this synchronization e.g. if an admin has removed an LDAP user from an LDAP group in the UI, the user will be re-added to the group when logging in again after the synchronization.

Note

This applies to groups created by LDAP in OMERO 5.1.x. Groups created in older versions of OMERO will not be registered as LDAP groups if you have manually altered their membership, even if the membership now matches the LDAP group.

omero ldap setdn true --group-name $NAME can be used to make these previous OMERO groups into LDAP groups.

## Legacy password providers

The primary component of the LDAP plugin is the LdapPasswordProvider, which is responsible for creating users, checking their passwords, and adding them to or removing them from groups. The default password provider is the `chainedPasswordProvider` which first checks LDAP if LDAP is enabled, and then checks JDBC. This can explicitly be enabled by executing the system admin command:

    omero config set omero.security.password_provider chainedPasswordProvider

When the LDAP password provider implementation changes, previous versions can be configured as necessary.

- `chainedPasswordProviderNoSalt`

  The `chainedPasswordProviderNoSalt` uses the version of the JDBC password provider without password salting support as available in the OMERO 4.4.x series. To enable it, use:

      omero config set omero.security.password_provider chainedPasswordProviderNoSalt

- `chainedPasswordProvider431`

  With the 431 password provider, the user filter is only checked on first login and not kept on subsequent logins. This allows for an OMERO admin to change the username of a user in omero to be different than the one kept in LDAP. To enable it, use:

      omero config set omero.security.password_provider chainedPasswordProvider431

See also

OMERO.server installation

  Installation guide for OMERO.server under UNIX-based platforms

Server security and firewalls

  Security pages for OMERO.server

LDAP plugin design

  Developer documentation on extending the LDAP plugin yourself.

What are your LDAP requirements?

  Forum discussion if you have LDAP requirements that are not covered by the above configuration

JNDI referrals documentation

  https://docs.oracle.com/javase/jndi/tutorial/ldap/referral/jndi.html

## Active Directory

Active Directory (AD) supports a form of LDAP and can be used by OMERO like most other directory services.

In AD, the Domain Services (DS) ‘forest’ is a complete instance of an Active Directory which contains one or more domains. Querying a particular Domain Service will yield results which are local to that domain only. In an environment with just one domain it is possible to use the default configuration instructions for OMERO LDAP. If there are multiple domains in the forest then it is necessary to query the Global Catalogue to enable querying across all of them.

### Global Catalogue

In an AD DS forest, a Global Catalogue provides a central repository of all the domain information from all of the domains. This can be queried in the same way as a specific Domain Service using LDAP, but it runs on different ports; 3268 and 3269 (SSL).

- LDAP AD Global Catalogue server URL string

      omero config set omero.ldap.urls ldap://ldap.example.com:3268

  Note

  A SSL URL above should look like this: ldaps://ldap.example.com:3269